Participation in many sports involves repeating certain motions over and over again. The consistent ability to perform these motions in a particular way is usually critical to good performance in the sport. Different methods have been found to help participants develop the ability to repeatedly move in a certain way. Increasingly, technology is being used in such methods to improve performance in sports.
Video analysis is an important part of modern sports training. The ability to see oneself perform a motion helps an individual identify flaws in technique and correct them. Furthermore, video analysis techniques can be applied to video of a sports motion to help identify aspects of a motion that need changing or identify aspects of a motion performed correctly for positive feedback.
Taking golf as an example, a golfer's swing technique is critical to their ability to strike a golf ball consistently and therefore perform well. Over the years, a preferred golf swing technique has been identified and most golfers strive to model their swings as closely as possible to this preferred technique. Video analysis has been used in golf to improve golfers' swings.
A straightforward form of video analysis is simply to record a golf swing and watch it back to identify flaws that cannot be discerned by the golfer themselves or by a tutor. Video footage can be paused so that individual frames showing a particular swing position can be analysed.
Another analysis method is to display a person's golf swing next to that of another, to more easily identify differences compared to a model swing. Some existing methods involve synchronising the two swings so that corresponding swing positions are shown together, which makes comparison easier.
To analyse a golf swing, it is useful to examine certain swing positions, such as the address position, top swing position, impact position and finish position. It is therefore desirable to identify the video frames showing the golfer in those positions.
When capturing video footage of a golf swing, there may be a large amount of footage recorded either side of the swing itself, for example when a player is preparing to swing. Such footage is largely redundant and can make it difficult to quickly identify the actual swing motion and may take up precious memory space in the case of stored digital video data. It is therefore desirable to extract segments of video footage that contain just the golf swing motion.
Some existing methods of golf swing video analysis achieve these aims, i.e. extraction of a segment of video containing a golf swing or identification key swing positions, or both. It will be readily understood that identification of the address and finish positions allows the segment of video showing the golf swing to be extracted: the golf swing is shown in the portion of video in between the address and finish positions.
Examples of such existing methods are:                Manually examining the video swing footage and identifying the segment showing the golf swing and frames showing key motion positions. This is time intensive as it requires a user to look through all the video footage.        Detecting the noise of impact to identify the moment of impact, as in U.S. Pat. No. 6,537,076 and U.S. Pat. No. 6,567,536. The rest of the swing is assumed to be within a certain time either side of this moment. This method requires an audio detection device working with the video capture device and is only able to accurately detect the impact position. This method will not reliably work for swings of different tempos.        Using other types of sensor to detect parts of the swing, for example pressure mats, as in US 2006/0281060. However, this method requires the use of another type of sensor, which may be expensive and not always be convenient.        Placing colour markers or other identifiable labels on the golfer and golf club and automatically detecting their positions in the video footage, as in U.S. Pat. No. 7,097,459, U.S. Pat. No. 7,704,157 and U.S. Pat. No. 7,857,708. However, this requires the use of markers or labels which may not always be available and errors may occur if the markers are not placed in the correct locations,        Using object recognition-based methods, such as identification of a player's silhouette or body segments, as in US 2010/0303303. However, these methods involve solving a difficult and time-consuming problem of human shape recognition before applying golf swing analysis methods. These methods are therefore very complex, require high levels of processing power/memory and take some time to product results.        Detecting the position of the ball in the video footage and how it changes during the motion, as in KR 101002846. While this method avoids the need for equipment beyond a video capture device and processor, it relies on the presence of a ball, which may not always be available. It also assumes the ball is covered by the club head during the address position and therefore is not useful for analysing video recorded from, an angle in which the ball is not covered by the club head at address. Finally, it estimates which frame shows the finish position by making certain assumptions which may not always be true.        
In another method of analysing a golf swing, the position of the golf club is detected using straight line detection methods such as Hough or Radon transforms, as in U.S. Pat. No. 7,200,282. Such methods may be useful for segments of video in which the golf club is relatively stationary but they may not work as effectively if the club is moving quickly and the image is blurred. These methods are also computationally intensive.
Many of the above techniques can also be applied to motion analysis in other sports.
It is therefore an object of the invention to provide an improved method of analysing video images of sports motion that overcomes at least some of the disadvantages discussed above.
Video capture devices have become increasingly widespread in recent years. Video images can be captured on many personal electronic devices such as digital cameras and mobile phones. It has therefore become very easy for anyone to capture video footage of an individual executing a particular sports motion. It would be convenient if the same device used to capture video footage could be used to analyse the footage. It is therefore an alternative object of the invention to provide a method of analysing video images of sports motion that can be performed by a personal electronic device.
It is an alternative object of the invention to provide an improved apparatus and/or system for analysing video images of sports motion
Alternatively, it is an object of the invention to at least provide the public with a useful choice.